In a belt type continuously variable transmission, when a foot brake switch (hereinafter, referred to as a brake switch) is brought to an ON state by a depression of a brake pedal, a braking torque is transmitted from driving wheels to the continuously variable transmission, so that a belt slippage may be generated. A patent document 1 discloses an art to prevent the belt slippage by increasing a belt clamping force of the continuously variable transmission when the brake switch is brought to the ON state.
In recent years, a hydraulic control of the transmission is often performed in a state where a line pressure is set to a low value, for improving fuel economy. In a case where the brake switch becomes the ON state when a vehicle travels in a state where the line pressure is lower than a pilot pressure that is a source pressure of a signal pressure for (of) various hydraulic actuators, an oil vibration may be generated due to the increase of the belt clamping force. That is, in a case where the belt clamping force is increased in a rage where the line pressure is lower than the pilot pressure, the vehicle behavior is varied due to the oil vibration even when the belt slippage.